Exhaust gas recirculation (EGR) is a technology used with internal combustion engines to reduce nitric oxides (NOx) in the engine exhaust. In gasoline engines, EGR has the further advantage of extending the knock limit.
The recirculated exhaust is often cooled using liquid or air coolant as a cooling medium to increase its effectiveness in reducing NOx. EGR coolers are designed with a certain heat transfer capacity to achieve the degree of cooling required to maintain the system's thermodynamic effectiveness.
Unfortunately, as exhaust continues to flow through the EGR cooler, deposits form and accumulate on the inside wall of the cooler. These deposits reduce the heat dissipation through the cooler's walls and on to its water jacket, thus reducing the cooler's effectiveness.